C4-6 perfluorinated glycol diesters of trimethylacetic acid



United States Patent Ofi 3,189,644 Patented June 15, 1965 ice 3,189,644 C PEHFLUGRENATED GLYCOL DIESTERS F TRIMETHYLACE'I'EC ACID Jonathan L. Snead and Henry Gisser, Philadelphia The esters listed in Table I were prepared by a commonly known and conventional method. Specifically, the esters were prepared by direct esterification by reaction of fluoroalcohol and acid in the presence of a mineral County, Pa., assignors to the United States of America 3 g g g 2* ig dwhlch g g gggi fi as represented by the Secretary of the Army n 6 Wa er L me was remove y re u 1 b m No Drawing. Filed Feb. 25, 1963, Ser. No. 260,922 a eels-Stark trap.

4 Claims. (Cl. 260-488) Studies were conducted on various samples of the pre- (Granted under Title 35, US. Code (1952), sec. 266) pared esters to determine oxidation stability at different 10 temperature levels. In this connection a dynamic test Th6 invention described herein may be manufactured was employed similar to that described in the federal and used by or for the Government f r governmental specification for Lubricants, Liquid Fuels, and Related urposes without the payment to 11s of any royalty fllfle- Products; Methods of Inspection, Sampling, and Testing on. VV-L79 1e, May 21, 1953, Method 5308.3 entitled Cor- This invention relates to improved fluoroalcohol esters 15 rosiveness and Oxidation Stability of Light Oils. In acim particular 3!, t0 flllofofllcohol esters Whlch exhibit 3 cordance therewith, duplicate 10 gram ester samples were oxidation and thermal stability and have a wide liquidus tested at temperatures ranging from 345 F. to 482 F. in range. the presence of copper, steel and aluminum catalyst strips The preparation of fluoroalcohol esters is disclosed in (1.750 x 0.375 x 0.025 inches). The t t were the prior art and the greater stability of Such est rs as ducted in an aeration-type glass apparatus through which compared with corresponding non-fluorinated e rs has clean, dry air was bubbled at the rate of 1.2 liters per been shown experimentally. However, the use Of fiu r hour. Efiluent gas was collected in an 0.1 N potassium al l esters i still limited y such stability, and In ny hydroxide solution. The usual criteria of induction peapplications more stability at higher temperatures is reriod (based on increase in acidity), changes in viscosity, quired. For example, many practical applications necesolor, etc. were employed to indicate stability. Results sitate exposure to temperatures of approximately 500 F. are given in Table At such temperatures the prior art fluoroalcohol esters are not oxidatively stable for more than very short periods of time, e.g., 24 to 72 hours, or are not sufficiently non- Table H volatile or do not exhibit a sufi'iciently wide liquidus range AT 3 47 F. for practical utility.

Accordingly, a principal object of the present invention is to provide fluoroalcohol esters which exhibit superior Neutralization number (eq. mg. oxidation stability. Ester Induction Viscosity KOH/gm.)

Another object of the invention 15 to provide fluoroal- 15%;? ifl ppea a e cohol ester which exhibit superior oxidation and thermal p volatile bili volatile Other objects of the invention will in part be obvious 7 24 37.8 39.3 26.7 Dark; sludge. and 111 part appear hereinafter 1n the detailed descript on. 3 168 o 0 O6 0 Clear; colorless The present invention involves the concept that elimi- 40 g 126 26 ,4. Amber, nation of secondary and tertiary carbon-hydrogen bonds i iig g-g 23%;?- from the acid moiety of fluoroalcohol esters results in 311 1:6 1:2 mbeg edi s improved oxidation and thermal stability.

During the course of the investigation on this invention, neopentyl and neopentyl-like chemical structures of acids AT were incorporated through synthesis into fluoroalcohol and fluoroglycol esters. Table I lists the various esters produced together with the several physical properties 2:: 122 2'; 81% 2:2 ;f3;; measured.

Table I AT 482 F. Vacuum boiling Refractive Density, N0. Ester point index (at' gins/cc. 168 2.8 1.9 2.8 Clear; colorless.

( CJmm 25 C.) (at 25 C.) 24 25 3. 9 8.6 Dark; sludge.

Hg) 168 3.6 2.6 1.1 Clear; colorless.

24 32 10.7 7.4 Dark; sediment. 168 1.8 4.5 0.9 Clear; colorless. 1 Tetrafluorobutyl-lA-bis 78/0. 35 1.3930 1.1192 24 42 8.6 4.5 Dark; sediment.

(trimethylacetate). 24 6. 6 3. 7 1. 4 Do. 2 Tetrafluorobutyl-lA-bis- 100/0. 35 1. 4047 1. 0085 168 --11.1 16.3 52 Amber.

(lti,3-dimethylbutyr- 72 l4.9 6.0 2.9 Dark; sediment. a 3 Hexafiuoropentyl-1,5- 86/0. 35 1. 3854 1.1852

bis (trimethylacetatc). *Based on viscosity at 100 F. 4 Hexafluoropentyl-LS- 108/035 1.3973 1.1609

li5dlmthylbu- 130131;.ggiifiliflkglglgi,lgiH-gctaifililflgpeilgq i;-methylglutalrate, an is o eca uoro ep y -me gutarate, disc osed 5 t s i 94/0-35 1-2512 by Faurote et al.: Journal of Industrial and Engineering Chemistry,

b5(mmethy1acet3t.e)- vol. 48, pp. 445454 (1956) and ester 12, a fluoroalkyl camphorate, dis- 6 octafluirohexyllis'bls Halo-35 1-3899 L223? closed by E. I. du Pont de Nemours: Product Information Bulletin g y y Stable Fluids-The l luproalkyl Camphorates, are representative of 7 Hexafluoropenty1 1,5 137m 8 1 3996 1' 1676 ggzgsprior art oxidativeiy stable fluids and are included for comparison bis(n-hexanoate). 8 Hexafluoropentyl-1,5- 13010.62 1. 3961 1.1647

)is(22)-dimethylbuyra e 9 BiflsflHillHifllidgdleca- 143/033 1.3528 1. 6140 Analysis and interpretation of the oxidation data of ggf g i Table II indicate that at the lowest test temperature (347 F.) there is a difference in stability among the in ester 3 supports the contention that the presence of a secondary carbon-hydrogen bonds afiect stability detrimentally. At 392 F. difierences in stability between ester 5 and esterf6 are apparent. This again supports the aforementioned contention since ester 5 contains no secondary carbon-hydrogen bonds while ester 6 contains four such bonds.

At 482 F. it is observed that a marked contrast exists between the fluoroglycol esters lacking secondary carbonhydrogen bonds and those containing such bonds. Perfluorobutyh, perfiuoropentyl-, and perfluorohexylacetate esters (esters 1, 3 and 5, respectively) were very stable and exhibited low increases in viscosity and acidity. At the end of 168 hours these esters were relatively unchangedclear, colorless and without sludgeor sediment. The 3,3- dirnethylbutyrates (esters 2, 4 and 6), however, were severely oxidized in less than'24 hours and exhibited high increases in viscosity and acidity as well as the formation of insoluble This striking difierence in stability is attributed to the presence of secondary carbon-hydrogen bonds in the latter esters which act as initial reaction sites for oxidative break-down. and 5 are much more stable to oxidation than prior art esters l1 and 12, in that the former have much longer induction periods, develop much less acid and exhibit no color change or sediment throughout the test period.

Considerable improvement in the oxidation stability of 600 hours during a prolonged oxidation test (1000 ,hours); 7

Several esters r'epresentative of those listed in Table I were tested for thermal stability. About 5 grams of each were sealed under vacuum in a nitrogen atmosphere in a Pyrex glass ampoule and maintained at 500 F.

Changes in Viscosity and neutralization number were used as criteria of thermal stability. The test data are set. forth in Table III below.

Similarly, inventive esters 1, 3

4 Table III Neutraliza- Ester Hours Viscosity tion number N 0. at 500 F. Final appearance change* increasejeq.

. (percent) mg.KOH/

" gm.) I

72 Clear; colorless -l U 0 72 Amber +0.6 0.7 168 Clear; colorless 0 0 Based on'viscosity at 100 F.

The inventive esters (esters -1 and gave no measurable decomposition even after 168 hours at 500 F. The

substantially complete lack of change in physical proper- 1 ties with respect to esters l and 3 as contrasted'with the 1. An oxidatively and thermally stable fluoroglycol ester having the structural formula: a

wherein n has a value of 2 to 4.- 2, The ester according to claim 1 wherein n hasa of 2. a

of 3. g a 4. The ester according to claim 1 wherein n has a value of 4. v a

ReferencesCited by the Examiner UNITED STATES PATENTS 3,049,557 8/62 Emrick 260 4106 X 3,081,342 3/63 Ver Nooy 260-485 3,115,519 '12/63 Crouse 'et 2.1. n 260-488 OTHER REFERENCES Filler et al.: J.A.C.S., 75, 2693-1697 1953 LORRAINE A. WEINBERGER, Primary Exztminer.

LEON ZITVER, Examiner.

value 3. The ester according to claim 1 wherein n has a value 

1. AN OXIDATIVELY AND THERMALLY STABLE FLUOROGLYCOL ESTER HAVING THE STRUCTURAL FORMULA: 